This application claims the priority of German application 101 57 514.9, filed Nov. 23, 2001, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method and a system for identifying a valve clearance of an internal combustion engine and for recording the actual position of a valve opening cam of an engine with or without a cam shaft adjusting system.
Usually, valve clearances on the load change indicators of internal combustion engines are only measured during regular inspections of the internal combustion engines and corrected, if necessary. Generally, inspections are done at intervals as recommended by the engine manufacturer (e.g. distance traveled or operating time). Another possible alternative for determining the inspection intervals is based on an evaluation and display device installed in a vehicle which, for example, registers the distance, operating time, and operating conditions of internal combustion engine usage (e.g. frequent cold start, short operation time, run time duration with heavy loads or revolutions per minute), analyzes the like, and, accordingly, indicates the necessity of an inspection.
None of these known systems considers the actual conditions of different components of the combustion engine, which are usually checked and adjusted in the course of an inspection. Since, when determining the time of the inspection, the actual condition of the components that are to be inspected and, if necessary, adjusted in their settings is not considered, and since this determination is made based only upon experiences and observations that were established on the basis of running distance or operating time, at best, while taking the operating circumstances into consideration, the inspection that is initiated in practice rarely occurs at the right time. In order to avoid damage to components, the inspection time is therefore normally selected such that, even with intensely stressful usage of the combustion engine, the inspection is performed before reaching a critical condition in order to prevent failures and the resulting cost of downtime and repair. Accordingly, the inspections usually occur too early, which causes unnecessary costs, especially when considering the total of all inspections in the life span of the internal combustion engine. Beyond that is the fact that unexpected changes, which necessitate an inspection, are not registered and reported. For example, it may not be detected when the valve clearance of the load change indicators changes excessively and therefore danger exists that further operation of the engine could result in damaging the internal combustion engine.
Beyond that, in internal combustion engines with or without cam shaft adjusting systems, the actual positions of the valve opening cams are conventionally detected with the help of position sensors on the cam shaft. This requires the existence of one or more sensors, transmitters, cabling, and analyzing circuits and software in a control unit. In view of the many necessary components for recording the actual position of the valve opening cam, such cam shaft adjusting systems are relatively complex and expensive.
One object of the present invention is to provide an improved method and system for recording the valve clearance of the load change indicators, and/or the actual position of the valve opening cams of the cam shaft. This can be realized, while avoiding costs for additional components, by being able to access the components already existing in the vehicle (e.g. sensors) in order to obtain information, about the valve clearance of the load change indicator and/or the actual position of the valve opening cam of the cam shaft. This task is accomplished by the features of the present invention.